Tapping screw

Abstract

It is possible to prevent a screwing torque from becoming excessively high even when a screw is threadedly engaged into a deep guide hole. In a tapping screw 100 comprising a parallel screw 22 , a taper thread 23 provided closer to a tip end of the tapping screw than the parallel screw 22 , and a plurality of projections 30 which partially project along an apex and flanks on both sides of a screw thread and which form an internal thread on a surface of a guide hole formed in a to-be fastened member, the plurality of projections 30 are provided from a region where the taper thread 23 is provided to a portion of a region where the parallel screw 22 is provided, and a diameter of a virtual cylinder which comes into contact with tip ends of some of the projections 30 including a projection provided in a region where the parallel screw 22 is provided is larger than an outer diameter of a external thread of the parallel screw 22.

1. A tapping screw comprising:
 a parallel screw; 
 a taper thread provided closer to a tip end of the tapping screw than the parallel screw; and 
 a plurality of projections which partially project along an apex and flanks on both sides of a screw thread and which form an internal thread on a surface of a guide hole formed in a to-be fastened member, wherein 
 the plurality of projections are provided from a region where the taper thread is provided to a portion of a region where the parallel screw is provided, and 
 tip ends of the projections in the taper threaded region extend beyond tip ends of the screw threads in the parallel screw region in a radial direction with respect to a virtual cylinder formed by the screw; 
 wherein a leading side of the flanks of the projections are thicker than the trailing side of said flanks of the projections. 
 
     
     
       2. A tapping bolt comprising:
 a parallel thread section; 
 a flange located at a head of the bold and attached to a shank of the bolt; 
 a taper thread provided closer to a tip end of the bolt than the parallel section of the bolt; and 
 a plurality of projections which partially project along an apex and flanks on both sides of a bolt thread and which form an internal thread on a surface of a guide hole formed in a to-be fastened member, wherein 
 the plurality of projections are provided from a region where the taper thread is provided to a portion of a region where the parallel thread section is provided, and 
 tip ends of the projections in the taper threaded region extend beyond tip ends of the screw threads in the parallel screw region in a radial direction with respect to a virtual cylinder formed by the screw; 
 wherein a leading side of the flanks of the projections are thicker than the trailing side of said flanks of the projections.